PCM digital audio syncing with GSM codec framing


#1

Good day experts,

We are interested in using the WS6318. From the technical manual I notice that there is a PCM digital audio interface. The WS6318 also supports 4 GSM audio codecs (HR, FR, EFR, AMR).

I have the following questions:

  1. Is it possible to somehow force the WS6318 to select a particular GSM audio codec or is this only selected by the network operator?

  2. Assuming that the EFR audio codec will be used in most cases if both the end-to-end devices are only 2G compatible (e.g. two WS6318 modules calling each other), would it be possible to sync the PCM digital audio with the EFR audio codec’s frames? In other words, the EFR codec encodes speech in 20ms frames of 160 samples, can I somehow determine where those 20ms/160 sample boundries are and pack my PCM samples exactly according to those boundries?

Thanks in advance!


#2

Hi,

No, it’s not possible to select the codec that is going to be used. The network provider is the one selecting the coded to be used.

The synchronization between the PCM samples and the codecs is fully controlled by the telecom stack, as it depends on the time when the samples will be sent towards the network (and that have to be encoded using the right codec). No possibility to change them by the user as it would disturb the behavior of the telecom part.

Thanks